The present invention relates to a push-pull arrangement for use in frequency multipliers, receiver mixers, signal converters or modulators, which work in accordance with the push-pull principle and which are modulated with the fundamental wave or a subharmonic component of the mixing/local oscillator.
An application of the push-pull principle to transistor mixers, both when working with subharmonic, as well as fundamental wave operating modes is described in chapter 9 of Steven A. Maas, Microwave Mixers, 2nd edition, Artech House, 1993, which is hereby incorporated by reference herein (compare FIG. 9.13, p. 335 and FIG. 9.16, p. 341). In previous design approaches, the power of the mixing/local oscillator is carried through simple phasing lines or through 180xc2x0 hybrids to the gate terminals of the field effect transistors FET (alternatively: base terminals in the case of bipolar transistors). As the result of unavoidable manufacturing tolerances, the transistors represent unequal terminations for these phase-control signals, which leads to different reflections and, thus, to unequal power distribution and unwanted phase relations. This difficulty can be overcome, but not fundamentally, by partially preconditioning the transistors, or only by allowing for substantial power losses.
An object of the present invention is to distribute the power output of the signal from the mixing/local oscillator, with the least possible outlay for components, in such a way that the transistors are able to be modulated with respect to one another with the same power and with 180xc2x0 phase shift, and that, in spite of manufacturing tolerances of the transistor parameters, the signal is effectively decoupled from the other signal gates of the circuit.
The present invention provides a push-pull arrangement, in which the power output of the signal from the mixing/local oscillator is distributed in such a way that the two transistors are able to be modulated with the same power and with 180xc2x0 phase shift wherein one selects the characteristic wave impedance of the phasing line, i.e., in the case of more stringent band width requirements, the characteristic wave impedance of a one- or multistage hybrid, to match the transistor input resistances and the circuit layout, and that provision is additionally made at the second transistor for a terminating resistor, which is either directly connected or by way of a line having matching characteristic wave impedance.
Accordingly, it is provided, similarly to the case of a traveling-wave amplifier (here, however, simplified to two transistors), to select the characteristic wave impedance of the phasing line, i.e., in the case of more stringent band width requirements, the characteristic wave impedance of a one- or multistage hybrid, to match the transistor input resistances. At the second transistor, provision is additionally made for a terminating resistor either connected directly or by way of a line having matching characteristic wave impedance. To reinforce this, the transistor input impedances can be preconditioned.
An advantage of the present invention lies in that manufacturing tolerances no longer result directly in pronounced changes in matching within a resonance structure, but rather mainly in a slight change in the phase relation of the modulation signals within a certain range of the manufacturing tolerances. One further advantageous embodiment of the present invention provides for the control inputs of transistors T1 and T2 to be provided with a circuit for matching input impedance. Here, the intention is to additionally compensate for any existing manufacturing tolerances of transistors T1 and T2.